In the field of medicine, it is often necessary to have an exact image of a body in order for example to plan and/or perform surgery or an irradiation treatment, wherein it is necessary to obtain the image as immediately before the irradiation and/or treatment as possible, since a body can significantly change even within short periods of time. Such images are predominantly obtained by means of cone beam computed tomographs (CBCT), since they represent relatively simple apparatuses for 3D imaging and only require a little time to prepare the image. However, because of the cone beam, they have the disadvantage of exhibiting only a limited detection range which often does not include the entire relevant region of the body. Moreover, their spatial resolution and dynamic range are lower than with fan beam computed tomographs (CT) or magnetic resonance tomographs (MRT).
In order to avoid this disadvantage, the U.S. Pat. No. 6,915,005 B1 suggests: preparing a CT image, chronologically before the CBCT image, which captures a larger region of the body than the CBCT image; aligning the CT image onto the CBCT image; converting the aligned CT image into a sinogram; and supplementing regions of the sinogram of the CBCT image outside the detection range of the CBCT image from the sinogram of the aligned CT image.